Here I have mentioned a method to download YouTube videos directly from Firefox. You just go to YouTube, watch a video, click a bookmark and the video starts downloading, without any software. Allow me to show you a method to download videos directly from YouTube using Google Chrome bookmarklet without using any software.

Make sure your Google Chrome browser always shows the ‘Bookmarks bar’.
You can click settings icon and check ‘Always show bookmarks bar’ option.
Right click on the bookmarks bar, and then select Add Page.

In the Name field, type “Download YouTube Video” or anything you would like for the bookmarklet name, and for the URL field paste the following javascript code: